Bob,

I don’t have sonics on the cold side.  Hoses come off inercoole and go to 3^rd intercooler.

Should there be sonics on the cold side?

Thanks,

Tim

 

 

I think you’ll see several advantages to turning them around.

 

Keep us posted…

 

BTW, do you have sonic nozzles in your “cold side” pressurization taps—the hoses leading to the third intercooler?

BOB

 

 

Bob,

I found my warm side sonics installed backwards (arrow towards intercooler not heat mixer).  This probably led to blowing the warm air hose off at the mixer.  Haven’t flown to altitude and selected heat since turning them around.

Thanks for the input.

Tim

 

 

Tim wrote:

 

Are there Sonics in the Cold side of the intercooler?  I don’t think so..  Does the longer length of the hoses and the 3^rd intercooler reduce flow/pressure ?

 

You are correct on not using sonic nozzles on the cold side of the intercooler. The exit air is much cooler, and therefore under much less pressure (recall Boyle’s Law), so full flow through the cold side tubes helps achieve a balanced flow between hot and cold temperature selection in the cockpit. Not the “scientific” way to achieve a flow balance, but it’s very simple and works pretty well—over the flow rates and pressures we’re using. And to answer your second question, the pressure and flow are not affected so much by the hose length and long flow path—which do contribute somewhat. The drop in temperature is responsible for the majority of reduced pressure/flow through the cold side.

To answer another question posed by an LML contributor: the concept of a “sonic” nozzle is that when the air passing through the nozzle reaches supersonic flow, it sets up a shock wave in the throat that effectively “throttles” the flow. This causes the nozzle to flow a relatively constant volume of air over a wide range of input pressure-once the flow reaches supersonic in the throat. Without these, you’d see a very abrupt change in cabin in-flow and pressure every time you move the throttle of your turbocharged Continental while the cabin pressure controller—a rather slow-acting device, struggles to keep up with the changes. If you install the sonic nozzles backward, they won’t work as intended, the flow will be closely proportional to the input pressure.

Hope this helps.

Bob Pastusek